Voltammetric co-determination of lead and copper in gunshot residue based on iron oxide particle/spent coffee...

A novel electrochemical sensor was developed for the detection of lead (Pb) and copper (Cu) ions using spent coffee grounds decorated with iron oxide particles (FeO/SCG). The FeO-decorated SCG was used to modify a glassy carbon electrode (GCE). FeO, SCG, and FeO/SCG were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of the modified electrode were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode modifications increased the active surface area and electron transfer and enhanced the accumulation of the target analyte. In the optimal condition, the developed sensor showed linear ranges of 1.0 µg L^-1-0.05 mg L^-1 and 0.05 mg L^-1-0.8 mg L^-1 for Pb²⁺ and 5.0 µg L^-1-0.1 mg L^-1 and 0.1 mg L^-1-0.8 mg L^-1 for Cu²⁺. The limit of detection (LOD) was 1.0 µg L^-1 for Pb²⁺ and 2.4 µg L^-1 for Cu²⁺. The developed sensor was successfully applied to determine Pb²⁺ and Cu²⁺ in bullet holes. The results were in good agreement with those obtained by inductively coupled plasma optical emission spectrometry (ICP/OES).